Advanced IP Network Design (CCIE Professional Development)

BGP in the Core

The core is the place in your network where the scalability pains will be felt first. The core needs to have full knowledge of all the destinations in the network—full routes. The task is to configure BGP on all the core routers, and let it handle the routes that are external to the core. The IGP will carry only the information about local destinations. See Figure 8-1.

A simple way to shift the burden of carrying the routing information to BGP is to implement a full iBGP mesh in the core. In this case, the routing information from the distribution layer is redistributed into BGP, which carries it as internal routes. IGP routes have a lower administrative distance than iBGP and, hence, are favored. Therefore, it is necessary to ...